Both open-loop and closed-loop multiple-input multiple-output (MIMO) schemes in the form of spatial multiplexing (SM) have been introduced in 3rd Generation Partnership Project (3GPP) long term evolution (LTE) Release 8 (R8) for downlink transmissions. Closed-loop spatial multiplexing refers to linearly pre-coded MIMO transmissions where either full or partial channel state information (CSI) is available at the transmitter. Open-loop spatial multiplexing corresponds to MIMO transmissions where CSI is not available at the transmitter or is partially available, (e.g., long-term measurements may be available but short-term measurements allowing fast adaptation are not). Open-loop spatial multiplexing is a good candidate for high mobility cases.